Memory devices provide data storage for electronic systems. One type of memory is a non-volatile memory known as flash memory. Many modern personal computers have BIOS stored on a flash memory chip. Such BIOS is sometimes called flash BIOS. Flash memory is also popular in wireless electronic devices because it enables the manufacturer to support new communication protocols as they become standardized, and to provide the ability to remotely upgrade the devices for enhanced features.
NAND is a basic architecture of flash memory. A NAND cell unit comprises at least one select gate coupled in series to a serial combination of memory cells (with the serial combination being commonly referred to as a NAND string). NAND is often formed as a memory array having a large number of memory cells arranged in row and column fashion.
Individual memory cells of a NAND array may be uniquely addressed during programming and erasing operations. However, in some applications it may be desired to deprogram (i.e., erase) all of the cells in the array. The cells may be grouped into blocks in such applications, and the NAND array may be erased by serially stepping through the individual blocks to erase the blocks one after another. It would be desirable to develop architectures which enable all of the memory cells of a NAND array to be erased in a single global operation instead of the conventional block erase operations.